Not an immigration lawyer but I unfortunately have to care about this stuff w/r/t a non-US nation and have previously had to care about it w/r/t the US on behal

Not an immigration lawyer but I unfortunately have to care about this stuff w/r/t a non-US nation and have previously had to care about it w/r/t the US on behalf of third parties: even "You talk at our office and we pay you a modest honorarium" requires a B-1 (short-term travel for business purposes to e.g. negotiate a contract) as opposed to e.g. a visa waiver. It is vanishingly unlikely that the duration and scope of this project, which looks an awful lot like "We wish to purchase your professional services for 3 months", would be sustained under the B-1 visa. Speak to a lawyer prior to relying on the above, etc.